% Moed 2010 A bio  MatlabBio 76623   12/7/2010
%% part A solution    
clc
clear
format compact

%%  1
A = [1 2 3;6 5 4;7 8 9] ;
B = (eye(3)*3)  | diag(min(A)) 
C = fliplr(~B) <  diag(diag(A)) 


%% 2
D = [1 2 3;7 5 3;4 3 2]  
M = D .* ones(3) 
Z = [diag(D')  diag(D)] * [1 ; 2]


%% 3   
r = linspace(2,10,5)
s = 8:-2:0
t = r .* s 
u = t + [2 3 4]*[-2 -1 2]' 


%% 4
a = 2:6
b = [ a>=mean(a) zeros(1,3) a(2:3) ]
b(2,8) = -3
x = any(b)


%% 5 
v  = 1:5
f = (v+1) > mean(v - min(v))
g = mean( find( f ))


%% sloutions:
%{ 
%% 1
B =
     1     0     0
     0     1     0
     0     0     1
C =
     0     0     0
     0     1     0
     0     0     1
     
%% 2
D =
     1     2     3
     7     5     3
     4     3     2
M =
     1     2     3
     7     5     3
     4     3     2
Z =
     3
    15
     6

%% 3
r =
     2     4     6     8    10
s =
     8     6     4     2     0
t =
    16    24    24    16     0
u =
    17    25    25    17     1

%% 4
a =
     2     3     4     5     6
b =
     0     0     1     1     1     0     0     0     3     4
b =
     0     0     1     1     1     0     0     0     3     4
     0     0     0     0     0     0     0    -3     0     0
x =
     0     0     1     1     1     0     0     1     1     1

%% 5
v =
     1     2     3     4     5
f =
     0     1     1     1     1
g =
    3.5000
 %}
-------------------------------------------------------------------------------------

function B = q1( A , k )
    % Moed 2010a   MatlabBio part B - q1)  
    if nargin<1
        clear, clc
        format compact
        A = reshape( randperm(16) , 4 , 4) - 8
        k = 2
    end

    B=A;
    [r,c]=size(A);
    dmax=max(diag(A));
    Amean=mean( mean(A) );

    % change B using 2 for loops
    for i=1:r
        for j=1:c
            if i==j && A(i,j)<0
                B(i,j) = dmax ;
            end
            if A(i,j)>0 && mod( A(i,j) , k ) == 0
                B(i,j) = Amean ;
            end
        end
    end

end
----------------------------------------------------------------------
function L = q2( M , z ) 
   % Moed 2010a   MatlabBio part B - q2)  
    if nargin<1
        clear, clc
        format compact
        M = magic(5) , z = 106 % is true ; z = 120 is false
    end

    [r,c]=size(M);
    count = 0

    % count 3x3 squares 
    for i=2:r-1
        for j=2:c-1
            if sum(sum( M(i-1:i+1 , j-1:j+1))) > z
                count = count + 1
            end
        end
    end

    countall = (r-2)*(c-2);
    L = count > countall/2;
    
end
-----------------------------------------------------
function u = q3(D)
% Moed 2010A   MatlabBio part C - q3) 
% q3 gets a matrix of integers D as input,
% and returns u. What is u?
% try  D = [2 12 0 7; 3 6 5 9]
[m,n] = size(D);

u = zeros(m*n,1);
i = 1;
for y = 1:n
    for x = 1:m
    	u(i) = D(x,y);
        i = i + 1;
    end
end


%{
 The solution for
D =
     2    12     0     7
     3     6     5     9
u = q3(D)

u =
     2
     3
    12
     6
     0
     5
     7
     9

Similar to the operation of: u = D(:)
%}